Mid-Piacenzian Warm Period

The Mid-Piacenzian Warm Period (mPWP) (prior to 2009 known as the Middle Pliocene Warm Period), or the Pliocene Thermal Maximum, was an interval of warm climate during the Pliocene epoch that lasted from 3.3 to 3.0 million years ago (Ma).

Climate

The global average temperature in the mid-Pliocene was 2–3 °C higher than today, global sea level 25 meters higher, and the Northern Hemisphere ice sheet was ephemeral before the onset of extensive glaciation over Greenland that occurred in the late Pliocene around 3 Ma. Near-surface permafrost extent was substantially lower relative to the present. Global precipitation was marginally increased by 0.09 mm/yr according to CCSM4 simulations. Annual Northern Hemisphere Hadley circulation was weakened, but annual Southern Hemisphere Hadley circulation was enhanced. As during the Quaternary glaciation, glacial-interglacial cycles existed during the mPWP and it was not a uniform and stable climatic interval.

Polar amplification during the mPWP was considerable. The mean annual temperature (MAT) of eastern interior Alaska was about 7-9 °C higher than its present day MAT of -6.4 °C. Palynological evidence from the Yermak Plateau in the Arctic Ocean shows that the thermophilic and moist boreal Tsuga-Thuja-Cupressaceae-Betula-Ilex community became dominant in the Arctic during the mPWP. At the lagerstatte of Camp del Ninots in northeastern Spain, a MAT of 14.3 ± 2.6 °C and a mean annual precipitation (MAP) of 846.8 ± 165.4 mm prevailed. The East Asian Winter Monsoon (EAWM) strengthened during the mPWP. The influence of the East Asian Summer Monsoon (EASM) did not extend as far into the interior of East Asia as it does today, causing a much drier climate to occur in the Chinese Loess Plateau relative to the present day. In the Nihewan Basin, a stable and warm climate predominated from 3.58 Ma to 3.31 Ma.